A buck converter (step-down converter) is a DC-to-DC power converter which steps down voltage (while stepping up current) from its input (supply) to its output (load). It typically contains at least two semiconductors (a diode and a transistor, although modern buck converters frequently replace the diode with a second transistor used for synchronous rectification) and at least one energy storage element (such as a capacitor, inductor, or the two in combination). To reduce voltage ripple, filters made of capacitors (sometimes in combination with inductors) may be added to such a converter's output (load-side filter) and input (supply-side filter).
The requirement profile of high performance synchronous buck converters demands high conversion efficiency over the entire load range. In order to achieve this, various measures need to be taken to reach proper behavior. As one of the requirements for proper efficiency, the FETs need to be switched as fast as possible. However, extremely fast switching may lead to voltage overshoots which might be out of the safe operating area of the device, i.e. the device may enter avalanche.